CT Scans: Are They Necessary to Evaluate Response to Therapy?

Date: December 20, 2007

Let’s face it, most of us get fixated on the monthly CBC numbers, more than we should.

Blood tests go only so far in monitoring the status of your CLL. For starters, CLL cells hang around in swollen lymph nodes, spleen and the bone marrow. Some patients have most of their CLL cells lurking in these “solid” locations, with barely a hint of the CLL in their blood counts. Others may have most of the cancer cells swirling around in the blood, with barely enlarged lymph nodes. Moral of the story, one shoe does not fit all and each of us has a unique fingerprint of how the disease manifests itself.

The 1996 NCI criteria spelled out the definition of what constitutes a complete response (CR), a partial response (PR) etc. The determination is made by looking at the blood counts in a CBC, as well as physical examination of the patient. The physician “palpitates” the patient, digging around with his trained fingers looking for swollen lymph nodes or spleen still remaining after therapy. A CR requires clean CBC, and no palpable nodes or spleen. Obviously, this physical examination is only as good as the experience of the physician, and even the best expert cannot get a sense of lymph nodes buried deep in the abdomen, for example.

That raised the question: should CLL patients be asked to go through a CT scan to look for lymph nodes that cannot be felt by the fingers of the physician? Would we get more accurate and quantitative data of the state of the disease remission by comparing CT scans before and after therapy? The engineer in me loves numbers, but sometimes number can lie too. For starters, I understand CT scans cannot tell the difference between a swollen lymph node that is choke full of CLL cells, and an empty lymph node with the architecture intact, but all the CLL cells dead and gone. It takes a while for the empty lymph nodes to gradually shrink back to their original size. It is also a fact that CT scans are expensive – both in terms of money as well as potential risk of radiation exposure, if one indulges in them with abandon.

So: here is the question, does it help to get CT scans or not? I think most of us would grit our teeth and get the darned scan, but only if it did some good, gave us a better and more accurate fix on things and that in turn helped us make better therapy decisions.

Here is the answer, from the perspective of Dr. John Byrd and the rest of the crew at Ohio State. The title of the article says it all. Sure, using CT scans to define the type of remission down-graded some of the CRs to PRs and so one down the ladder. Think of it as tougher grading on the curve with CT scans, more grade inflation when response definition is done by physical examination. But the bottom line is not what they call the remission, what matters is whether the additional information is of practical use. According to Byrd, et al., there do not seem to be grounds for routine use of CT scans to judge therapy response.

For those of you who participate in clinical trials there may be no choice. Many of the new clinical trials have built-in testing via CT scans and bone marrow biopsies. You have to agree to these tests as part of the clinical trial protocol. But for the rest of us who are getting treated in our local oncologists’ offices, it may be a good idea to push back just a tad, if our guy is a little too gung-ho about ordering CT scans. You may want him to tell you why he thinks it is a good idea to get that extra CT scan.

Be well,

Chaya
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Abstract

J Clin Oncol. 2007 Dec 10;25(35):5624-9.

Computed tomography scans do not improve the predictive power of 1996 national cancer institute sponsored working group chronic lymphocytic leukemia response criteria.

PURPOSE: National Cancer Institute-sponsored Working Group (NCI-WG) response criteria for chronic lymphocytic leukemia (CLL) rely on physical examination, blood, and bone marrow evaluations. The widespread use of computed tomography (CT) scans has prompted many to advocate for the incorporation of this test into CLL response criteria.

PATIENTS AND METHODS: In a retrospective review of 82 CLL patients treated at the Ohio State University (Columbus, OH), we compared CT assessed response using non-Hodgkin's lymphoma (NHL) response definitions with NCI-WG response.

CONCLUSION: Current NCI-WG CLL response criteria are a significant predictor of PFS in previously treated CLL patients, with no additional benefit from the inclusion of CT scans. Although retrospective, these results highlight the importance of prospective validation of CT scans before routine inclusion in CLL response criteria.

PMID: 17984187
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